ACTRESS, writer and comedienne Sharon Horgan is responsible for some of the best but most underrated sitcoms of recent times – including Pulling and the superb Dead Boss.

In Secrets of a Good Marriage here she takes on a more factual role as she investigates what makes a winning formula for the perfect marriage.

She talks to six couples to find out the secrets of their fulfilling relationships, and a bride and groom who are about to tie the knot.

Among them are two couples, Chas and Diane, and Jo and Graham. They have all lived together in the same house for 23 years. The two women are identical twins, and their four children have been raised as siblings.

There is also tantric sex teachers Kavida and Roland; Chris and Norma, who have a 32-year age gap between them, and Louella and her partner, who tolerates her having a lover. It seems happiness has no strict template.